When Sen. Barbara Mikulski of Maryland retired two years ago, Rep. Donna Edwards gave up her safe Prince George’s County congressional seat to take on her House colleague, Montgomery County’s Chris Van Hollen, in the Democratic primary. Ms. Edwards lost by nearly 13 points, in part because a supportive outside group ran a negative and wildly inaccurate ad in the final weeks of the campaign that backfired on her.

Ms. Edwards‘ campaign seemed to consist of the idea that she deserved support because she would be the first African-American Maryland senator and only the second black woman to sit in the Senate. Like Hillary Clinton, Ms. Edwards blamed her loss not on any personal shortcomings, but on the Democratic Party establishment, the old boys network in Maryland, special-interest money, and white male racists who couldn’t stomach the idea of a black woman senator.

Ms. Edwards had launched her campaign as the darling of the left and a champion of identity politics. She began her career by beating a senior black Democratic congressman, Albert Wynn, who had made the mistake of hiring her to work in his congressional office. His sin was that he had born male. His colleagues, perhaps in retaliation for what they saw as her unfair attacks on a friend, denied her the Congressional Black Caucus backing that year.

Those who knew and have worked with Ms. Edwards have been taken aback by her unbridled ambition and willingness to do anything to win. Like many politicians, she saw the House as but a place to catch her breath before moving onward and upward. Her ambition ranks ahead of other considerations as she claims that a commitment to principle drives her. Men and women like Ms. Edwards can be found in both parties, and they are not an attractive lot; they are recognizable by their willingness to do anything to reach the next rung on the political ladder.

As a member of Congress, Ms. Edwards was quick to identify with the downtrodden, but didn’t accomplish much. She tended, in fact, to neglect her own constituents. Liberal Rep. Gerry Connelly of Fairfax County, Va., just across the river from her Prince George’s congressional district, said during the 2016 Senate primary that Edwards voters were voting for “somebody who’s going to bask in her own feelings of moral superiority.”

After that defeat, Ms. Edwards vanished except for occasional interviews but soon decided to resurrect her career by running for county executive in Prince George’s County. She was no doubt shocked when potential challengers appeared, including a formidable black woman in her own right, Angela Alsobrooks, the county’s state’s attorney. By April, Ms. Alsobrooks, who is widely known and respected in the county, was leading Ms. Edwards by 10 points and seemed headed for victory in the June 26 primary.

Since Ms. Edwards‘ opponent this year is not white, male or conservative, Ms. Edwards is relying as she did two years ago on help from her friends “outside” the campaign. It arrived just last week in the form of a well-funded barrage of negative ads portraying Ms. Alsobrooks as a crook. The ads are being run by a group called We Are Prince George’s, which, according to press accounts, has already spent more than $600,000 in support of Ms. Edwards and is expected to increase the negative attacks in the next few weeks.

As a Prince George’s resident, I realize that any number of former Democratic officeholders are serving time. The county is, after all, one of the most corrupt in Maryland and perhaps the country. Allegations of corruption leveled at an incumbent officeholder like Ms. Alsobrooks might be expected to gain traction, as Ms. Edwards supporters hope.

That hope may not be realized in Ms. Alsobrook’s case. Neither the Edwards campaign nor her union backers have failed to produce even a smidgen of evidence to back up what are increasingly being seen as false charges. Negative attacks on one’s opponent can work, but they must have some connection with reality or are likely to backfire. Ms. Alsobrooks is a well-respected prosecutor with a clean record who has fought the corruption that plagues the county, and many observers are beginning to suspect that today’s Edwards campaign, like the campaign of two years ago, will be hurt rather than helped by her supporters.

Ms. Edwards may be a living, breathing example of the truth in the old saying that those who refuse to learn from their mistakes are doomed to repeat them.